Method for reactivating bone-char and the like



1952 E. D. GILLETTE ET AL 2,616,858

METHOD FOR REACTIVATING BONE-CHAR AND THE LIKE Filed March a, 1946 Z6 1210 SPENT g/ 51" w .32 v CHAR INLET 712; I I -Jif y;

JPEN CHAR 570F465 J0 7 5 URNER l Y FURNACE 60015 FRESH c/Mfi V I SPENT01ml? Z9 10 INLET 31/ 2 was r: FINES sue/m 83 r--,---- 4/01/01?PERCOLAT/O/V AND 4 WASH TAN/(s,

ACTIVATED V565 mam cARao/v 111i 5 MIX TANK 2d cum F/L 75R CAKE INVENTORSEARL DWIGHT GILLETTE THOMAS M. BROWN ATTORNEYS V COOZER fiatentecl Nov.1952 UNITED STATES PATENT OFFICE EarlDjwight Gillette,Hastings-ori-Hudson, and Thomas M; Brown, Bronxville, N. Y., assignorsto Refined Syrups & Sugars, 71nd, Yonkers; N. Y., a corporation of NewYork Application March 6, 1944;, Serial No, 652,460

1 Claim.

This inventionrelates to methods and apparatus-for reactiv'atin-gfiltering material and the like such, for enampl'e, as spent moistbonehar which has been used for decolorizing or otherwise refining sugarliquors or other mat'erials;

In the refining of sugar liquors, syrups; and the lili'epit has ulnabeen the practiceto treat the sa e in percolation tanks or otherwise,with bone char for decoloriz'in'g purposes or the removalof otherundesired ingredients. Such bonechar as customarilyused comprisesaporous tricalciu iri 5 phosphate material in 'finely dividedcondition,the orous surfaces'being covered with a thi n layerofc'arbon (surfacechar is usually 14-60 mesh). Usually the bone-char as commerciallyavailable for these purposes comprises in the neighborhood of from 8 to10% carbon. After each use of the bone-char for this purpose i'thas'formany years been the custom to reactivate the char by allowing it tofallthrough tubes which are heated externally to a temperaturesuch thatthe decolorizing properties of the char are more or less restored,However, repeated treatment of the char in this way results intheaccuniulation therein of higher and higher percentages of carbon. Yetwhen the carbon content'ireache's even as high or higher than 11% thematerial hasbeen found to be definitely unsatisfactory for'tre'atingsugar liquors. As such unsatisfactory condition progresses with thereuse "ofthe' char,-it becomes necessary to use larger" and largeramounts ofchar in order to maintain thedes'ired color in the charfiltered liquor. The" mixture becomes sorelatively ineffectivethat incommercial practice heretofore it has been found necessary to useanamount of bone-char ranging'from' about 3 5 up to as high as 160% ofthe amount of sugar being treated (by dry weight). Since such bone-charand the reactivating thereof is'costly, the use of it in such largeproportions, with the necessity of constantly adding considerable freshquantities, results in aheavy expense' which has not'heretofore beenavoidabledespite various efforts which have been made to try to do' so.For example, in some cases it is the practice after the char has beenreactivated a number oftimes to subject it to a kiln treatment forburning off a subsantial propor-ti'on of theexcess carbon. However, thispractice-as usually carried out has the disadvantage that duringintermediate periods the char is relatively inelficient; also thepercentage of re,- mainingcarbon cannot be properly controlled and insome'parts of the char nearly all of the carbon may be burned outso thatthesep'ortions are thereafter inactive; Furthermore, despite thesereactivating and decarbonizin'g steps as heretofore practicedthe charmasses havea very objectionable odor, generally noticeable throughoutthe plant, and this" results in imparting an odor orp o s'sibly otherundesirable'qualities to the sugar liquor. It-appears' thatin aconventional char kiln" where the bone -char passes through elongatedtubes and where the char has'probably a'thic'kness' in thesetubesrangingfr'om l" to 2" that only theparticle's -of charin contactwith the inside of th'e tubes becomes reactivated; the bulk of thecharpas'sing through the entire kiln wit-h out sufli'cient heattreatment to either reactivate the carbon on the char'or'to dispel theimpurities from the char.

According to the present invention a method and apparatus is providedfor so reactivating the bone-char that its carboncontent maybe'maintained at the desired optimum value and at the sametime'eliminatingall objectionable or noticeableodors, With thisinvention it has been found that the" amount of bone-char us'ed'fordecolorizing sugar, for example, may be reduced to a quantity amountingto about 1'1 to 12% of the amount of sugar. At the same time, the amountof char lost with each"reactivat'ion thereof is no more than from A to/2 of one percent so that the corresponding percentage of make-up charrequired to be added to the reactivated char represents a very minorexpense as compared with the prior practice. Furthermore, the resuitingsugar liquor astreated with the char: reactivated in accordance with theinvention is' free of odor so that so far as concerns removal'of odorsno subsequent vegetable carbon treatment would be required although forfinal clear ole colorizationsub's'equent treatment with a smallerquantity of activated vegetable carbon is desirable.

When: organic matter, of the type which the I Various further and morespecific objects, features and advantages of the invention will appearfrom the detailed description given below taken in connection with theaccompanying drawings which form a part of this specification andillustrate merely by way of example, preferred form of apparatus for thepractice of the invention. The invention consists in such novelfeatures, arrangements and combinations of parts and features as may beshown and described herein.

In the drawings:

Figure l is an elevational view showing somewhat schematically anarrangement of furnace apparatus for carrying out the invention;

Fig. 2 is a similar view of a modified form of the apparatus; and

Fig. 3 is a flow sheet schematically indicatin the manner in which thebone-char may be utilized and reactivated in a plant for treating sugarliquor in accordance with the invention.

With the apparatus shown a substantially continuous supply of spentmoist bone-char may be introduced through an inlet I0, at the top of afurnace H, as from a conveyor l2. The furnace may comprise a pluralityof superposed hearths as at I2-l9 inclusive, contained within asurrounding cylindrical furnace wall as at 20. The furnace may be of thewell-known Herreschoff type having a central rotatable shaft as at 2|,carrying rabble-arms as at 22 extending out over each hearth and allcarrying rabble-teeth as at 23, for periodically agitating and graduallyadvancing the material over each hearth. Alternate hearths are formed,respectively, with central and peripheral discharge openings as at 24,25, so that the material may be rabbled inwardly and outwardly,respectively, on alternate hearths and allowed to fall fromhearth-to-hearth through said discharge ports.

The rabbling structure may be rotated in the usual way as by motordriven gearing 26. Also cooling air cavities may be provided through therabbling structure in the usual way, the air being admitted as through aconduit 21 connected to the base of the shaft. The air after passingthrough the cooling conduits may be withdrawn through a conduit 28 fromthe top of the shaft, as by a suction blower 29.

For purposes of explaining the operation of the apparatus in accordancewith the invention,

the furnace may be considered as being divided into four zones, asindicated in Figure 1, two hearths being shown for each zone, althoughit will be understood that depending upon the diameter and desiredcapacity of the furnace and other factors, each zone if desired mightcomprise only one hearth or might comprise more than two hearths. Alsothe functions of each of these zones to a certain extent may overlap.The first or upper zone will be referred to as a drying zone. Ordinarilythe material on the two hearths I2, [3 of this zone, respectively, maybe subjected to gas temperatures in the neighborhood of 300 and 460 F.When subjected to these temperatures, as the bone-char is being rabbledover these two top hearths, substantial quantities of moisture andgenerally the greater part of the moisture thereof will be evaporatedand may be drawn off through an outlet conduit 30 connected into theconduit 28 and thus to the suction blower 29. A damper as at 3| may beprovided accompanied by a manometer as at 32 for the conduit 30. Thedamper, for example, may be adjusted so as to provide 4 a gas pressureat the furnace outlet for example of .45" H2O.

The next or second zone will be referredto as a heating zone. On hearthsI4 and i5 therein the bone-char may be subjected to gas temperatures forexample in the neighborhood of 460 and 690 F., respectively.

At this zone outlet conduits as at 33, 34 are provided having dampers asat 35 so that adjustable amounts of the relatively drier atmosphere ofgases may be withdrawn from this zone and passed through a dustseparator or classifier as at 3B. In this classifier the excessivelyfine particles of bone-char and carbon are removed and passed to astorage container as at 32', whereas the withdrawn gases will passthrough a conduit 38, drawn by blower 39 which discharges the samethrough a conduit 40 into a combustion chamber 4! in a mannerhereinafter described.

The next, or third zone, will be referred to as aburning zone. Here thebone-char which will previously have become substantially dry, issubjected to hot gaseous products of fuel combustion coming from thecombustion chamber 4|. As will be hereinafter explained these hot gasescontain a limited and controlled amount of oxygen and also preferably asmall amount of water vapor in excess of such water vapor as may occuras a part of the products of combustion of the fuel. The temperature ofthe gases at hearths l6 and l! respectively may be maintained, forexample, in the neighborhood of 1080 and 1170" F. On these hearths mostof the organic material in the bone-char is burned away, together with acontrolled amount of the carbon preferably so as to restore the carboncontent to an amount comparable to or somewhat less than that present infresh bone-char.

The combustion chamber 4| may comprise a housing preferably somewhatelongated in a horizontal direction as shown, and formed of or linedwith suitable refractory material. This chamber may be supported by anysuitable means with one end thereof against the external wall of thfurnace, there being provided openings as at 42, 43 for bringing thisend of the chamber into communication with the spaces over hearths l6and H. An oil burner as at 44 may be mounted to extend through the outerend wall of the chamber to direct its flame toward the furnace opening42, 43. Oil and air lines for the burner respectively are indicated at45, 46, each provided with suitable valves for regulation of the oil andair mixture and the size of the flame. A plurality of conduits as at 48may extend from th conduit 40 into and through the end of the combustionchamber 4| at spaced points as shown, surrounding the centrallypositioned oil burner. Thus the flame in the chamber will be surroundedby jets of gases from the conduits 48 so that the walls of the chamberare protected against deterioration by the heat and at the same time thegases reintroduced through the conduits 48 become uniformly mixed withthe gaseous products of fuel combustion as the mixture enters throughthe openings 42, 43 into the furnace.

After passing through the third zone, the treated bone-char may bepassed over additional hearths l8 and [9 of the fourth zone at which thegas temperatures, for example, may be in the neighborhood of 875 and 850F. respectively. If desired, this fourth zone may be omitted although itis believed that in some cases a further beneficial effect in activatingthechar isjmade possible by reason of maintenance of the" relativelyhigh temperature thereof during the: short additional period of passagethrough such a fourth zone.

From the bottom hearth IS the material may pass out through an exitopening as at 50 into a suitable cooling device as at El, which may besupplied with cooling fluid through conduits as at 52, 53. The specificconstruction of this cooling device forms no part of the presentinvention, various suitable devices for this purpose being commerciallyavailable. As the material passes through externally cooled tubes orcavities thereof, it will become cooled before dropping out, forexample, onto a conveyor as at 54. In order toprevent any danger ofignition or injury of the carbon on the bone-char upon its discharge tothe atmosphere from the furnace; it should be preferably first cooled toa temperature of 300 -F. or less.

Summarizing the operation of the above de scribed equipment, the spentmoist bone char which may initially have a moisture content of about .22to 25%, is subjected to a uniform and rapid drying action in the firstzone with preferably the greater part of the moisture content beingdrawn off directly through the conduit 33. Because of the relativelyslow rotation of the rabble arms over the hearths, the rabble teeth willperiodically and gently advance each portion oI thetrelatively thinhorizontal layer of material on each hearth so that the drying action inthe first zone, as well as the treatment in subsequent zones, will beuniform for all of the material and insure that-all parts of it arerepeatedly exposed to the atmosphere of gases over each hearth.

In the second zone, the bone-char will become rather thoroughly driedand heated up to a temperature ready for prompt burning action in thethird zone. The gases as drawn off through conduits 33 and 34 from thesecond zone will include some of the moisture evaporated off in thiszone, whereas the remainder will pass on up to the first zone. Hot gasesfrom the burning zone will rise up into the second zone and act tomaintain the desired temperatures therein and then partially travel upinto the first zone for maintaining the drying temperatures therein, theremainder passing out through the conduits 33, 34 for eventual return tothe combustion chamber M.

The separation of the dust or fines as by the classifier 36, from thegases withdrawn from the conduits 33, 34 is highly desirable, sinceotherwise such dust .Would tend to adhere to and ac-- cumulate to aprohibitive degree on the interior walls of the combustion chamber andof the furnace burning zone. In any event such fine material isgenerally of such a nature that it would be detrimental to thereactivated bone-char if returned to the furnace and mixed with the chartherein. The classifier thus located in the gas recycling conduitprovides a simple means for continuously eliminating much of theobjectionable fines and dust from the product during its reactivation.

The oil burner, for example, may be operated in a. manner whereby itsfiamewill be at a temperature in the neighborhood of 300 0 F. When thegaseous products of combustion therefrom become mixed with the recycledgas entering through conduits 48, the temperature of the resultingmixture upon entering the furnace openings 42 and 43 may, for example,be in the neighborhood of 1600 F., assuming that the gases overh'earthsl6 and I1 are;to be maintained at about 1080 and 1 F. The recycled gasesmay for example comprise an amount by weight equal to about three timesthe amount oflthe gaseous products of combustion from the fuel burner.The oil and air supplies to the burner may, for example, be adjusted soas to provide about 2 of O2 in the combustiongases. This will providethe limited amount of oxygen required for burning away the organicmaterial from the char and a portion only of the carbon thereon, in theburning zone.- A relatively small amount of this oxygen will be utilizedinthe burning zoneso that the gases as withdrawn through the conduits33, 34 before recyclingmay have an 02 content of nearly 2 The varioustemperatures and othernumerically specified factors giveri herein arefora preferred example which has given unexpectedly satisfactory results,but itwill be appreciated that-these factors-may be variedconsiderablyin practice. For example, if a greater percentage of oxygenis made available in the burning zone, the temperature may be reducedsomewhat or, if the temperatures are-increased, then in general theoxygen present in the burning zone should be reduced.

With a furnace as above described of 'a diameter of 13% feet, it wasfound that three tons per hour of spent bone-char could be readilyreactivated, the speed of the rabbling structure being" adjusted at arate to cause that amount of materlal'to be passed through the furnaceper hour.

It is believed that the above described arrangement for recycling thegases from the furnace back into the combustion chamber is highlyadvantageous, not only because of its affording a ready means forcarefully adjusting and controlling the temperatures and gas mixture atthe burning hearths, but also because it provides a means for supplyinga controlled and limited amount of moisture in the form of superheatedsteam in the presence of the bone-char while it is beingreactivated.

Due to the effect of the presence of superheated steam during thereactivation of the carbon on the bone-char, its properties as'adecolorizing agent appear to be substantially improved. Since the gasesare preferably withdrawn through conduits 33 and 34 at intermediatehearths on which some moisture, but not an excess amount, is beingevolved, it will be apparent that means is afforded for reintroducingwith the combustion gases a continuous regulated and limited supply ofsteam. Such steam may for example constitute in the neighborhood of15-20% of the gas mixture introduced at the burning hearths. Thispercentage may be varied by adjustment of the dampers 35. For example,if more moisture is desired in the recycled gases, the damper in conduit33 may be'adjusted to a position relatively more open than thedamper inconduit 34. On the other hand, if drier recycled gases are desired, agreater percentage thereof may be withdrawn through conduit 34 by movingthe damper in conduit 33 toward closed position.

A manometer tube as at 60 may be connected tothe combustion chamber toenable determination of the gas pressure therein. In a typical case, themanometer reading was .35" E20. This pressure may of course be adjustedby adjustment of the blowers 29, 39 and the various dampers.

' Extensive tests have shown, as hereinabove stated, that the carboncontent of the bone-char should be reduced during the treatment to afigure below 11%. Considerably improved results are obtained if thecarbon content is reduced to about 9%. Furthermore, it has been foundthat satisfactory results may be obtained within rather wide limitsbelow 9%. It appears that best results for clear decolorization may beobtained with bone-char having from 3 to 7% of carbon, whereas from 2 to9% may be stated as the outer limits for reasonably economical andpractical purposes. 1 7

The above described equipment provides an efficient and economicalarrangement to operate, in that the spent wet char may be fed incontinuously and with the continuous delivery of cooled regeneratedchar. Also the time of treatment may be readily adjusted by adjustingthe speed of the rabbling structure so that the conditions of time,temperature and concentration of gases at the burning zone may all becontrolled, and by trial these factors may be adjusted to secure bestresults.

Fig. 2 shows an alternative furnace arrangement in which certain of theparts corresponding to those of Fig. 1 are identified by the same reference numerals accompanied by prime marks. Except as to featureshereinafter described, the arrangement of Fig. 2 may be the same as ofFig. 1. In Fig. 2 it will be noted that the lower two hearths have beenomitted so that the burning zone is at the bottom of the furnace withthe combustion chamber 4| correspondingly positioned. With this form ofthe invention, the

cooling conduits within the central shaft 2 I may be blocked off as by aplate 70 so that cooling air is not admitted to the rabbling structureat the relatively lower temperature hearths above this point. Instead ofproviding an independent source of cooling air, a part of the gaseswithdrawn through conduit 33 are conducted from conduit 40' through aconnection 'Il into the base of the shaft 2|. This portion of the gasespasses up through the central shaft and out through the hollow rabblearms as at 12 at the lower hearths. These rabble arms are thus kept at asafe temperature by these gases passing therethrough, the gases beingdischarged through suitable apertures or the open ends of the arms as at13. It will be understood that various dampers may be provided in theconduits, as indicated, to regulate the amount of gas withdrawn byblower 39 and the proportion thereof which is returned to the combustionchamber 4 I as compared with the proportion which is returned in to thefurnace by way of the cooling conduits of the lower rabble arms.

As indicated in Fig. 3, the reactivated bonechar, after passing from thefurnace 20 through cooler 5!, may be allowed to fall on a suitablescreen as at 80 for the discharge of waste fines into a hopper 8!. Thedesired reactivated char, together with such fresh make-up char as maybe needed, may then be conducted into a char storage chamber 82. Fromthis chamber the char may be discharged into alternatively usedpercolation and washing tanks as at 83, 84 containing the sugar liquorto be treated. From these tanks the treated liquor may be run into atank as at 85 for mixing with a desired quantity of activated vegetablecarbon for further clear-decolorizing treatment. After treatment in thistank the clear syrup and filter cake may be separated in a filter 86.The spent char in the percolation and washing tanks after removal of thesugar liquor, may be conveyed to a spent char storage chamber as at 81,where it is kept until fed into the reactivating furnace.

While the invention has been described in detail with respect toparticular preferred examples, it will be understood by those skilled inthe art after understanding the invention that various changes andmodifications may be made without departing from the spirit and scope ofthe invention, and it is intended therefore in the appended claims tocover all such changes and modifications.

What is claimed as new and desired to be secured by Letters Patent is:

Method for reactivating spent moist bone char which comprises passing acontinuous supply thereof successively through drying, preheating andburning zones by periodically agitating and gradually advancing the charin generally horizontal layers through each zone and allowing same tofall from zone to zone.'continuously introducing into the burning zone astream of hot gaseous products of fuel combustion together with steam,maintaining about 15-20% of steam, and a suflicient oxygen content, inthe atmosphere in said burning zone to cause burning away of the organicmaterial on the char but limiting such oxygen content to about 5% orless so that carbon will remain in and upon the char in amounts of about2-9%, continuously conducting the gaseous products from such burningzone into the presence of the char in the preheating zone to providesuificient heat for causing steam to be there evolved from the char,continuously withdrawing from said preheating zone a substantial part ofsaid gaseous products and steam and, after separating dust therefrom,reintroducing same into said burning zone along with said gaseousproducts of combustion in an amount and at a temperature such as tomaintain a temperature of about 900-1170 F. in the burning zone.

EARL DWIGHT GILLETTE. THOMAS M. BROWN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 343,666 Lillie June 15, 1886351,929 Lillie Nov. 2, 1886 1,114,371 Laist Oct. 14, 1914 1,440,194Wijnberg Dec. 26, 1922 1,598,967 Hiller Sept. 7, 1926 1,806,020 Parkeret al. May 19, 1931 1,833,590 Read Nov. 24, 1931 1,895,878 Bunce et alJan. 31, 1933 2,064,813 Andrews Apr. 24, 1933 2,277,355 Roderick Mar.24, 1942 2,333,111 Lykken Nov. 2, 1943 2,387,936 Nicholls et a1 Oct. 30,1945 2,433,498 Whitford Dec. 30, 1947 2,457,837 Simpson et a1. 1 Jan. 4,1949

